Variable resistance



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VARIABLE RESISTANCE Original Filed Dec. 5, 1955 ATTOR EY.

Patented Feb. 2, 1943 VARIABLE RESISTANCE Erwin R. Stoekle, deceased,late of Milwaukee, Wis, by Lillian Stoekle, executrix, Milwaukee, Wis,assignor to Globe-Union Inc., Milwaukee, Wis, a corporation of DelawareOriginal application December 5, 1.935, Serial No.

1941, Serial No. 391,478

(Cl. 20l55) Claims.

This invention relates to an improvement in variable resistors adaptedto be advantageously employed in combination with a power switch for usein a radio receiver or similar electrical sound reproduction apparatusalthough also capable of use as a variable resistor alone in radioreceivers or in other diverse applications.

The present application is a division of the application of Erwin R.Stoekle, filed December 5, 1935, Serial No. 53,139, for Combinedvariable resistance and switch.

The object of the invention is to simplify and compact the structure ofthe resistor, render it more reliable and eiiicient in operation, affordthe maximum range of adjustment, and make it practical to manufacture itwith economy from materials and by means of facilities ordinarilyavailable.

Among the more specific objects of the invention are to provide animproved and simplified means for holding the resistor and terminals ofthe variable resistance in place; and to improve the adjustable contactthereof and th manner of mounting, biasing, and adjusting the same, as

well as the means employed for conveying current thereto.

Other objects and advantages reside in certain novel features of theconstruction, arrangement, and combination of parts, which will behereinafter more fully described and particularly pointed out in theappended claims, reference being had to the accompanying drawing forminga part of this specification, and in which:

Figure 1 is a view in longitudinal cross section taken on line ll ofFigure 2 and illustrating 1 one construction in which the variableresistance of the present invention may be embodied;

Figure 2 is a view in transverse cross section taken on line 22 ofFigure 1 and looking in the direction of the arrows;

Figure 3 is a group view in perspective illustrating the resistor, itssplit-clamping ring, the tapered terminal for maintaining the partsassembled, and the conducting ring carried by the terminal;

Figure 4 is a fragmentary detailed sectional view taken on line 44 ofFigure 5; and

Figure 5 is a view in elevation looking toward the left of Figure 1 butshowing the device as it appears with the metal housing cup and parts ofthe variable resistance removed or omitted.

Referring to the drawing it will be seen that in the embodiment of theinvention therein illustrated, the variable resistance is contained inthe housing, designated generally at H.

While the 55 Divided and this application May 2,

housing H may be made in various ways, it is illustrated, for the sakeof example, as made up in part of a shallow metal cup 45, to the innerface of the body of which a flat disc 46 of insulating material issecured. The insulating disc 46 may be secured in place by the upsetinner end 41 of a mounting bushing 48 which is in this way alsoconnected to the apertured central portion of the body of the cup 45.The housing for the resistance also includes an annular body member 49of insulating material, a portion of which telescopes into the metal cup45. A resistor 50 is provided and may comprise a flexible strip having aresistive coating applied to its inner surface. The strip 56 ispositioned against the inner wall of the annular housing member 49 andis secured in position by means of a split expansible clamping ring 5|,which may be made of laminated, Bakelite sheet or other insulatingmaterial or composition of appropriate elasticity or resiliency, andwhich has one of its side faces positioned against the inner side of aninturned annular flange 49 integral with one end of the body member 49.A locating rib, which may be integral with the housing member 49, orwhich may be in the form of a fiber key so tightly driven into a key-wayprovided therefor in the housing member 49, engages between the ends ofthe resistor 50 to locate the resistor in proper position in the housing49.

Terminals 52 and 52' are electrically connected with the ends of theresistor 50 and project exteriorly of the resistance housing H. Theterminals 52 and 52, save that one is of the right and the other of theleft hand, are of identical construction, and, as shown in Figure 4,each has an angular portion 52 accommodated in an opening 49 provided inflange 48 and also in a groove 49 formed in the inner side face of saidflange 49*, the annular portion 52 of each of the terminals having anappropriately shaped extremity 52 snugly engaging the adjacent portionof the resistor 58.

The outer periphery of the ring 5| adjacent the split is notched as at5H to accommodate the inner extremities 52 of the terminals 52 and 52'so that the ring 5 when expanded, not only holds the resistor 59 butalso the terminals 52 and 52 in place. Suitable means is provided forexpanding the ring 5| so that its periphery clamps the resistor againstthe inner wall of the annular housing member 49 and the terminals 52 and52 against the resistor. In the present instance it is proposed toutilize a third terminal 54 for this purpose, and to adapt the terminalto perform this function it is tapered, as clearly shown in Figure 3. Inthe assembly, the tapered portion of the terminal 54 engages in notches55 and 55' formed in the confronting ends of the ring 5| at the splitthereof. Thus, the tapered terminal 54, by forcing the ends of the splitring away from each other at the split, brings about the desiredexpansion and clamping of the resistor and the other two terminals. Theterminal 54 may be formed integral with a conducting ring 51 which isdisposed against the inner side face of the split ring 5|.

The movable contact of the variable resistance includes a ring-likestrip 58 of spring metal and of good electrical conductivity. The stripis disposed adjacent or against one side face of a rotatable carrierdisc 63 of electrical insulating material, and while the strip 58 may besupported on and fixed to the disc 63 in various ways, this ispreferably and advantageously accomplished by forming an attachingtongue 65 integral with the disc, inserting the tongue 65 through a slot66 in the disc 83, and clenching, bending, or otherwise suitablysecuring the tongue to the disc 63.

The strip 58 has a portion 59 bent and intensioned laterally from themean plane of the strip to provide a collecting shoe which wipes againstthe conducting ring 51 and provides for passage of electric current fromthe conducting ring 57 to the strip 58.

The strip 58 is provided with an enlarged portion Bil which is formedwith an arcuate or semicircular notch 6i to snugly receive and have goodelectrical contact with a contact member proper, designated as at 62. Inthe particular construction shown in the drawing, and which is selectedmerely for illustration or example, the contact member 62 is in the formof a roller or short cylinder having rounded ends, the periphery of theroller bearing directly against the resistive coating of the resistor50. The enlarged portion 60 of the strip 58 is intensioned outwardly soas to insure good electrical contact between itself and the movablecontact member 62 and between the movable contact member 62 and theresistor 50. The particular form of movable contact member 62 may,however, be varied, as this form is not an essential feature of theinvention. For example, the portion 60 of the strip might in lieu ofbeing notched be itself fashioned or shaped to constitute the movablecontact member proper and to have direct wiping engagement with theresistor 50. In such event the roller 62 would be omitted entirely.Moreover, the particular formation of collector shoe 59 may be varied.The

important and essential characteristics of this feature of the inventionreside in the contact strip 58 and in the way it is combined with theconducting ring 51 and the resistor 50. The strip 58 is so constitutedthat it intensions the movable contact member proper radially outwardlyinto proper electrical contact with the resistor, and it intensions thecollecting shoe portion thereof laterally in a direction at right anglesto the direction of bias of the movable contact member and intoengagement with its conducting ring. A movable contact having a springstrip of this character is of particular advantage in connection withdevices which are produced in quantity or on a commercial scale sincethe parts may be properly fabricated and intensioned at the factory, anduniformity of action is insured inall of the devices put out. Uniformityof action is of particular advantage or especial importance in variableresistance of this character. The strip 58 may be stamped or cut outfrom a single piece of metal into a pro-formed, properly shapedsub-assembly, with parts thereof precisioned intensioned and ready forfinal assembly.

Where the construction is such that the movable contact proper takes theform of roller 62, then the insulating carrier 63 has a portion of itsperiphery slightly enlarged and provided with a notch 61, which receivesa portion of the roller 62, the assembly being such that the walls ofthe notch 61 of the disc 63 perform the function of transmitting angularmovement or adjustment to the movable contacting member 62, that is, thedisc 63 drives the contact member 62 and leaves to the spring strip 58only the duty of applying the requisite outward radial pressure to themovable contact and of conveying the electrical current thereto from theterminal 54 and conducting ring 51.

The disc 63 has a non-circular opening in its center which is snuglyfitted on 2. correspondingly formed inner end portion 64 of an operatingshaft 64 supported for rotative movement in the bushing 48 andconstrained against any axial movement by the provision of a shoulder 64on the shaft engaging one end of the bushing 48 and by the assembly heldon the inner end of the shaft by its upset end 64*. This assemblyincludes the carrier disc 63, just described, an appropriate springwasher 48 and a conical cup-shaped shield 90, which will be hereinaftermore fully described.

With the construction as thus far described, current flows throughterminal 54 and conducting ring 51 to the shoe 59 at one end of thestrip 51 and thence through the strip 58 to the roller contact 62. romthe roller contact 62 the current flows through the resistor to theterminals 52 and 52'. The amount of resistance incorporated in thecircuit depends upon the angular position of the contact 62 with respectto the resistor 50, and this, of course, may be conveniently adjusted byturning the shaft 64.

In the construction shown in the present application the adjustableresistance has a power supply switch, designated at 10, combinedtherewith. While this is advantageous in many instances, it is notessential, as the variable resistance of the present invention may beused therewith or without a power supply switch, and as the parts of thepower supply switch per se form no part of the invention of the presentapplication, they will not be described in detail. For a completedescription and disclosure of such a power supply switch reference ismade to the application of Erwin R. Stoekle, for Combined variableresistance and switch, filed December 6, 1935, Serial No. 53,139.

While one construction in which the invention may be advantageouslyembodied has been shown and described, it is to be understood that theconstruction shown has been selected merely for the purpose ofillustration or example, and that various changes in the size, shape,and arrangement of the parts may be made without departing from thespirit of the invention or the scope of the subjoined claims.

It is claimed:

1. A variable resistance comprising a housing having a curved innerwall, a resistor disposed against said wall and comprising a thin,flexible strip having a resistive coating applied to its inner surface,a separate split clamping ring disposed within the housing and adaptedto be expanded outwardly to engage the inner periphery of the resistorand clamp the resistor against the wall of the housing, and means forexpanding the split ring outwardly including a tapered terminalcooperable with the ends thereof.

2. A variable resistance comprising a housing having a curved innerwall, a resistor disposed against said wall and comprising a thin,flexible strip having a resistive coating applied to its inner surface,a separate split clamping ring disposed Within the housing and adaptedto be expanded outwardly to engage the inner periphery of the resistorand to clamp the resistor against the wall of the housing, and means forexpanding the split ring outwardly including a tapered terminalcooperable with the ends thereof, in combination with terminalscooperable with the resistor and having portions disposed between thesplit ring and the resistor whereby said terminals are clamped againstthe resistor by said ring.

3. A variable resistance comprising a housing having a circular wall, aresistor disposed against said wall, an operating shaft rotatable withrespect to said housing, a carrier disc of insulating material disposedwithin the housing and fixed to said shaft, a curved strip of springmetal of good electrical conductivity disposed adjacent a sideface ofthe disc and secured thereto so as to be supported thereon and rotatabletherewith, said strip having a portion thereof intensioned radiallyoutwardly and having a contact member pressed into wiping engagementwith the resistor under the influence of said radially intensionedportion of said strip, a conducting ring mounted on the housing to oneside of the strip, said strip also having another portion intensionedlaterally from the mean plane of rotation of the strip and toward theconducting ring and having a collecting shoe in wiping engagement withthe conducting ring under the influence of said laterally intensionedportion of the strip, and terminals connected to the resistor and tosaid conducting ring.

4,. A Variable resistance comprising a housing having a circular wall, aresistor disposed against said wall, an operating shaft rotatable withrespect to said housing, a carrier disc of insulating material disposedwithin the housing and fixed to said shaft, a curved strip of springmetal of good electrical conductivity disposed adjacent a side face ofthe disc, said strip having an integral attaching tongue, said dischaving a slot in which said tongue is inserted and secured to supportthe strip on and fix it to the disc for rotation therewith, said striphaving a portion thereof intensioned radially outwardly and having acontact member pressed into wiping engagement with the resistor underthe influence of said radially intensioned portion of said strip,conducting ring mounted on the housing to one side of the strip, saidstrip also having another portion intensioned laterally from the meanplane of rotation of the strip and toward the conducting ring and havinga collecting shoe in wiping engagement with the conducting ring underthe influence of said laterally intensioned portion of the strip, andterminals connected to the resistor and to said conducting ring.

5. A variable resistance comprising a housing having a curved innerwall, a resistor disposed against said wall and comprising a thin,flexible strip having a resistive coating applied to its inner surface,terminals engaged with the resistor, a separate split ring havingnotched ends adapted to engage the terminals and having its peripheryadapted to engage the inner peripheral surface of the resistor, saidsplit ring being adapted to be expanded outwardly to clamp the terminalsagainst the resistor and to clamp the resistor against the inner wall ofthe housing, and means for expanding the split ring outwardly includinga tapered terminal cooperable with the ends thereof.

LILLIAN STOEKLE, Executrix of the Estate of Erwin R. Stoekle, Deceased.

